The present invention relates to a method for a fully-automatic control of a galvanic deposition of copper coatings in galvanic acid copper baths.
Galvanic baths, which are particularly used for the deposition of shiny coatings for the strengthening of conductor paths of printed circuits, are during operation subject to a continuous consumption of their substances and must therefore be continually additionally supplied with dosed amounts of materials to be deposited, for obtaining even deposition conditions and to achieve a desired quality of the coatings being deposited. To obtain this it is necessary to preliminarily determine a corresponding metal ion concentration in individual substances of the bath so as to an insufficient or excessive dosing. During the determination of a metal ion concentration by analytical methods or by measuring of conductivity it has been defined that it was necessary to control and restore a required concentration of those substances which carry out such important function as gloss-forming substances or inhibitors.
These substances are also continuously consumed during the current application to the bath; the control of this consumption has been specifically difficult because it has to do with the mixture of a plurality of organic substances which exist in various, and also in very low, concentrations and disaasemble and decompose in accordance with their nature.
One of conventional methods of producing coatings in a galvanic acid copper bath is disclosed in applicant's U.S. Pat. No. 4,181,582.
It has been already proposed to determine an actual condition of the galvanic bath by analytical methods, in which the evaluation of substances has been carried out by a plate-even-integer method or by measuring of voltage ("Plating and Surface Finishing", 65, 1978, 5/60 f, and 69, 1982, 3/62 f). The utilization of these methods has been described in DE-OS No. 2,757,458. With these methods two reference electrolytes must be used; these evaluation methods have been utilized in the galvanic bath, however discontinually, and a continuous working proess with these methods has been impossible.